And despite both Obi-Wan and Yoda seeing Anakin as irredeemable, they saw fit to teach him how to do this?
They both told Luke Anakin couldn't be rescued from the Dark Side. Luke proved them wrong. Why
wouldn't they show Anakin mercy by letting his ghost see his son and daughter be happy?
No matter how you slice it, Vader's "Redemption" is hardly "good writing" compared to the stuff about Reva complained about.
LOL, bullsh*t. It's good writing in the sense that it gave his character a clear arc and satisfying and definitive ending. He knew the path he was on was irredeemably corrupt, hence his offer to Luke to overthrow his master and rule the galaxy as father and son, but he was too corrupt to return to the noble Jedi way by himself. Addicted to anger because of his hurt and longing, he kept trying to bring Luke down the same path, but, when faced with the choice between watching his master kill his son, and killing his master, he finally found the strength (with, yes, more than a bit of selfishness) to choose the latter, at the cost of his own life.
This is simple stuff, maybe, but remember: Vader only had
34 minutes of total screen time in the OT, and spent most of that time hearing reports, giving orders (and strangling people), and fighting. Again, a clear arc with satisfying and definitive ending.
If
this IMDb page is to be believed, Reva gets approximately 37 minutes of screen time in
Kenobi S1, and not only are her motivations
spectacularly incoherent, her character arc is explicitly
in no way resolved: Obi-Wan says "You have chosen not [become Vader]. Who you become now, that is up to you." How much guilt will she feel for her decades of misdeeds, and how much will she ascribe to the toxic patriarchy of the Sith? Will she decide to atone, and if so, will she do so quietly, through inner reflection, or with action? Unless Lucasfilm decides to revisit the character, her arc is objectively incomplete. She goes from trying to kill a child for borderline nonsensical reasons to deciding not to in the span of a few minutes, and then effs off, the end.
It's true that TV characters aren't necessarily
intended to have complete arcs the way movie characters in a trilogy are, but even taking that into account, if you think the quality of characterization writing for those two is in any way comparable...